Transmission



May 6, 1952 F. R. MCFARLAND TRANSMISSION 2 SHEETS-SHEET 1 Filed March16, 1946 CCL Ctrl! May 6, 1952 F. R. MCFARLAND TRANSMISSION 2vSHEETS-SHEET 2 Filed March 16, 1946 AL-s/ Patented May 6, 1952 UNITEDSTATES PATENT GFFI'CE TRANSMISSION Forest R. McFarland, HuntingtonWoods, Mich.,

assignor to Packard Motor Car Company, De-

troit, Mich., a corporation of Michigan Application March 16, 1946,Serial No. $514,907

(Cl. 'I4-472) 8 Claims. 1

This invention relates to motor vehicle transmissions and to controlmeans therefor.

In one type of transmission planetary gearing is controlled` by brakinga reaction member to establish geared drive and by clutching two membersto establish direct drive. Mechanism is usually provided to beconditioned bythe driver for selecting. forward; or reverse drive andneutral. The braking and clutching selections are usually automaticallycontrolled afterthe driver has first conditioned the transmission foroperation by forward or reverse selection and manipulation of theaccelerator pedal beyond idling position. Provision is also. usuallymade for overruling the automatic selection of the speed ratio in thegearing by movement of the accelerator pedal beyond wide open throttleposition. Thus the accelerator pedal and the shift selector are operatedby the 'driver and the balance of the control of the transmission isautomatic except for the shift at the will of the driver from high speeddrive to geared drive.l

An object ci' this invention is to provide a transmission controlmechanism of the character referred to in which a shift lever and anaccelerator pedal are actuated in series to condition the gearing fordriving.

Another object of the invention is to provide a transmission of thecharacter referred to in which direct drive is automatically effected bya vacuum 2 and speed responsive valve device in a fluid control systemto shift up in the speed selection and such drive is maintainedeffective by fluid pressure, in the control system below the value atwhich the upshift was made.

Another object of the invention is to provide a transmission of thecharacter referred to with control valves for establishing two diiferentdriving speeds that are responsive to pressure conditions in the engineintake manifold.

Still anotherI object of the invention is to provide a transmission ofthe character referred to in which braking and clutching are controlledby a duid system in which valves are automatically operated and in whichfluid pressure, when energizing the clutching device, assists inmaintaining the braking valve in open relation whereby the reactionmember in the gearing will always be ready to establish geared ldrivewhenever high speed drive becomes ineffective.

Other objects of the invention will, appear from the followingdescription taken in connection with the drawing, which forms a part ofthis specification, and in which:

Fig. i is a sectional view of a transmission and 2 control meanstherefore incorporating the invention;

Fig. 2 is a fragmentary Sootional View of the one-way brake for the.gearing taten on line 2-2 of Fig. 1;

Fig. 3 is an elevational View of o portion of amotor vohiolo Showing.tho, general. arrangement of the controls for the.' transmission: and

Fie- V1: is a diagrammatic and partly .Sectional View of the, Qontrolsystem for the transmission- Tho. transmission is, housodin oosios lfSooorod to one one of intorno-l Combustion eosin@ H- Tho enginecrankshaft l2 is ooonoobod with mpeller I3 of a ijuid coupling device I4in which power is transmitted to 1'wo runoors'oomrrsng,

rotors l5 and i6 and ooooontrio power or drive shafts Il and i8., Adriven shaft if) aligns with the drive shafts and means is provided fordrivlos the driven Shafts ,from the drive Shafts. at @Wo reduced speedsthrough two soar trains This driving means isI in the form of'planetarygearing in which gears 2KB and g! are nxed respectively to shafts il andi8, and gear 22 is fixed to driven shaft I9. Planet gears 2K3, 24 and 25mesh respectively with gears 20, 2l, and 22 and are rotatably mounted ona pin `22V' iixed to a carrier 2 5. The planet sears are shown formed asa unitary Structure'but they may be formed separately and xed togetheras a unitary structure.

Drive through either one of the planetary gear trains at a speed lessthan that oi their drive shafts is obtained by engagement oi a brakedevice 21 for holding the carrier to prevent reverse rotation thereof.The carrier has an extension 28 surrounding hub 2S oi a sectionalreaction member 3D and a one-way roller broke 3l. is. o1'- rangedbetween extension 28 and hub 29. Brake band 32 is anchored to casing l0in relation to.`

be engaged with or released from the reaction membr 30 by an actuatorpiston 21' and linkage 2 8. Engagement of the brake device will preventretrograde rotation of the carrier whereupon drive is transmittedthrough the driving means from either one of the drive shafts to thedriven shaft at a reduced speed. One-.way clutch 33 provides a drivingconnection between rotor i5 and sleeve 34 splined to shaft Il'. Thisclutch permits shaft 1'! to overrun rotor l5 when rotor i6 is effectiveas, the driver. At low engine speeds the primary rotor I5 will be thedriver and at some accelerated speed of the engine the secondary rotori6 will take over the drive.

A Ycliutch device 35 is operative to connect impeller II 3 directly withthe carrier whereby the driven' shaft I9 is rotated atsubstantially thesame speed as the crankshaft I2. A clutch hub 36 is splined to shaft 4|and the clutch plates 31 are slidably splined to clutch hub 36 and tothe carrier 26. The clutch actutor plungers 38 are arranged in anextension 39 of the carrier and are operable by a fluid pressure toengage the clutch plates. .Springs 40 in the carrier normally exertpressure to move the actuators away from plate engaging relation. Thedriving connection between the clutch hub 36 and impeller I3 includesthe shaft 4| splined to the clutch hub and to hub 42. The impeller hasplate members 43 fixed thereto and coil springs 44 provide a drivingconnection between the plates 43 and the hub 42.

When the clutch is engaged, the carrier is driven directly by theimpeller I3 so that power will flow from the carrier through the planetgears to the driven shaft I9. At the same time rotor I will be drivingshaft |1 so that the high speed gear train will be effective to alsodrive the driven shaft IS through the planetary gearing. This two-pathdrive will cause rotation of the driven shaft at substantially the samespeed as that of the crankshaft.

Tail shaft 45. extends into the driven shaft I9 and is splined toreceive an annulus gear 46 that surrounds sun gear 41 splined on thedriven shaft I 9. Planet gears 43 mesh with the sun gear. and theannulus gear and are rotatably mounted on a shiftable carrier 49. Thecarrier is provided with clutch teeth 50 adapted to engage with teeth onbrake plate 5| fixed in chamber 52` in casing wall 59. Carrier 49 is ro-"tatably mounted on sun gear 41 but is secured therewith againstrelative axial movement. The sun gear has internal clutch teeth 52adapted to mesh with the splines 53 on the tail shaft. By shifting thecarrier axially to the left, as

viewed in Fig. 1, teeth 50 may be moved into en? gagement with the teethon plate 5I to cause a reverse drive from shaft I 9 to shaft 45. Whenthe sun gear and carrier are shifted to the right, teeth 52 will engagewith the splines 53 on the tail shaft to provide a direct drive fromshaft I9 to shaft 45. In intermediate or neutral position of the sungear and carrier, teeth 58 will be disengaged from member 5I and teeth52 will be disengaged from splines 53.

A synchronizer brake 54 is arranged to hold shaft I9 stationary withplate 5I in order that teeth 59 may be shifted into engagement with theteeth on plate 5| without clash. This synchronizer brake consists ofplates 55 arranged in a chamber 52' in which actuator pressure ring 56is located. This actuator is normally moved to brake disengagingposition by spring 51. The geared drive brake device 21, the clutchdevice -35 and the synchronizer brake device 54 are applied by apressure fluid system. In such system there is a pump 58 driven from theimpeller shaft 4I and having an inlet conduit 59 open to the bottom ofcasing I8 and having an outlet conduit 6| terminating in a pair ofbranches 62 and 63. The branch conduit 63 leads to the synchronizerbrake actuator 56 and the branch conduit 62 supplies fluid to the geareddrive brake device 21 and the clutch device 35.

The uid flow through the branch conduits 62 and 63 is under control ofthe shift mechanism for establishing forward or reverse drive. Shiftlevel' 55 is pivoted to, casing I9 at 66 and has an arm 61 for movingshaft 68 in an axial dilrection. YThis shaft carries a yoke 69 arrangedto fit into a recess 19 in carrier 49. This shaft Cil also provides avalve for controlling the flow through branch conduit 62. One end ofshaft 68 traverses the branch conduit 62 and is formed with a pair ofspaced recesses 1I adapted to register with the branch conduit to permitfluid flow therethrough when the shifter yoke is in reverse or forwarddrive positions. When the shifter yoke is in neutral position flowthrough branch conduit 62 will be blocked off. Thus the drive selectingmechanism serves to allow fluid ow from the pump to the brake and clutchdevices 21 and 35 when in forward or reverse positions.

The branch conduit 62 is connected with a valve device 13 and conduit 14leads from the valve device to the brake device 21. The valve devicecomprises the casing 15 in which valve 1G is shiftable to control theflow between the outlet passage 11 and the inlet passage 18. There is avent passage 19. The valve is connected by stem 8l] with a'diaphragm 8|extending across the chamber 82 and spring 83 is arranged in thischamber to exert pressure against the diaphragm to normally move thevalve 16 to closed position shutting olf flowbetween passages 18 and 11.

Branch conduit 62 also leads to valve device 84 and conduit 85 connectsthe valve device with the clutch device 35. This valve device 84comprises a casing 86 in which a valve 81 is axially movable. The valvehas flanges 88 and 89 of different diameter and a connecting stemportion of less diameter than the smaller flange. The conduit 62communicates with inlet passage and conduit 85 communicates with outletpassage 9I, these passages being parallel and opening into the portionof the casing in which the large diameter ange 89 of the valve 81 isslidable. The larger diameter fiange of the valve controls flow betweenpassages 90 and 9| and is normally moved to close passage90 by spring 92bearing against diaphragm 93 secured to valve 81. The diaphragm definesa chamber 94 in which the spring 92 is housed. The valve is moved in anopening direction by two forces, one of which is responsive to Vehiclespeed and the other of which is responsive to pressure in the intakemanifold 95 of the engine II. A conduit 96 leads from the intakemanifold to chamber 94. A speed responsive bell crank or governor 91 ispivoted on a bracket 93 fixed to shaft 99 on which is xed a gear |89meshing with gear IUI on the tail shaft. The bell crank also has an arm|02, and spring |83 extends between this arm and the bracket 98 to exerta force opposing centrifugal force to which the bell crank is subjectedby rotation of the shaft 99. An arm of the bell crank rests against theupper end'l of valve 81 and as centrifugal force increases the bellcrank pivots so that the bell crank arm, opposite arm |02, moves valve|31 downwardly to open passage` 98 to passage 9|. The pressure ofcentrifugal force on the Valve and manifold pressurev acting on thediaphragm combine to shift the valve 81 toward open position but suchforces are opposed by spring 92. Spring 92 exerts a predetermined forcetending to close the valve and this force must be overcome by thevforces acting in the'opposite direction against the valve in order toconnect conduits 62 and 85 so that fluid may flow to the clutch device35. The arrangement is such that the valve will open when the vehicle istraveling at a speed around 12 miles per hour.

As previously stated spring 83 acting against diaphragm `8| tends tohold valve 16 closed so that fluid cannot flow from conduit 52 toconduit 14r and under this condition the reaction member 30 isl releasedso that there will lbe no drive through the planetary gearing providedthere is no sub-atmospheric pressure in chamber |32. Conduit 95'connects chamber 82 with bore |05 in the boss |04 which is open to theintake manifold and a valve device is arranged in the boss bore. Valve|06 (Fig. 3) is axially movable in the boss bore and there is a flange|61 on the valve engaged by spring |53 normally urging the valve toclosed position. Arrangement is made to open the valve in conjunctionwith operation of the accelerator pedal |08 of the motor vehicle pivotedat |09 to the iioor board H. Linkage I I extends from the acceleratorpedal to a shaft H2 on which throttle Valve H3 is fixed and rotation ofthis shaft is effective to cam the valve |06 open when the throttlevalve is opened beyond engine idling position. Cam H4 is fixed on shaftH2 and is arranged to engage a valve operating lever pivoted to theengine at H6. When the accelerator pedal is in idling position thethrottle valve I |3 is substantially closed and when in such positionthe cam H4 is ineffective to open the valve normally closed by spring|433. As soon as the accelerator pedal is depressed beyond idlingposition the caml H4 presses lever H5 down thereby opening valve |05 sothat subatmospheric pressure in the intake manifold will influence thediaphragm associated with valve 16. Thus it will be seen that valve 1Scontrolling fluid flow to the brake will be closed when the acceleratorpedal is in idling position and will be opened by the sub-atmosphericpressure in the manifold communicating with chamber `32 and acting uponthe diaphragm 8| as soon as the accelerator pedal is depressed foraccelerating the engine. Thus the shift lever valve and the acceleratorpedal controlled valve are in series and both must be open before fluidcan ow to the brake-device 21 to establish drive through the planetarygearing. With the brake device 21 applied, the carrier 26 will be heldstationary and low speed drive through gears 2li, 23, 25 and 22 willoccur when rotor I5 is eifective and a higher speed gear drive willoccur when rotor I3 is effected through gear train 2 l., 2li, 25 and 22.When the vehicle speed influence and sub-atmospheric pressure combine toovercome spring 92 so that valve 89 will open passage 90 to passage ilI, which is approximately at the vehicle speed of l2 miles per hour,fluid will flow to the clutch device 35 to establish direct drivethrough the planetary gearing as previously described. When valve 81 hasopened, the pressure of uid against the larger diameter flange 89 servesas an additional force with the centrifugal force and sub-atmosphericforce acting to hold the valve 31 in open position. This additionalforce of fluid pressure will maintain the valve open Ibelow the governedspeed of 12 miles per hour and thus will delay closing of the valveuntil a speed below the governed speed is reached. This fluid pressureeifect on the valve 81 will prevent hunting that is, opening and closingmovement when the speed of the vehicle is approximately l2 miles perhour and it also delays shift back from direct drive to geared drive ata speed below the governed upshift speed.

When valve 81 is moved axially due to the combined .effect of speed andvacuum, the iiange 88 closes a vent 88-a, and the flange 83 opens thepassage 90, thereby permitting fiuid under pressure to flow into thepassage 3| through conduit to actuate the plunger 3B of the direct driveclutch device 35 and thus: establish direct drive. The. carrier 26. willoverrun the reaction member 30' dueto the overrunning brake connection3| and thus the reaction member is always held ready to again establishgeared drive immediately upon closing of valve 81. Valve 16 remains openso long as the accelerator pedal is depressed beyondI idling position,due to the sub-atmospheric pressure in chamber 82, and it is alsomaintained in open position when the valve 81 is open through means. offluid pressure in the conduit leading to the clutch device 35. A conduitH1 leads from conduitv 85 to passage IIS in casing 15 so that fluidpressure in conduit 85 will act to press valve 16 toward open position.This added pressure acting to open valve 16 when the fluid pressure line`85 to clutch 35 is open will insure that the brake. device 21 isapplied so that geared drive will automatically become effectivewhenever the clutch control valve 81 is closed to vent the clutchdevice. 35 through the vent passage B13-a thereby disengaging it.

Provision is made for overruling the clutch control valve device so thatgeared drive may be established at the will of the driver. Means underthe control of the driver is provided to move the valve 81 upwardly toclosing position even though the intake manifold force and thecentrifugal force. dictate that the valve should be open. One means ofobtaining this overruling of the clutch valve control device consists ofelectrically energized means under the control of the accelerator pedal.Such means includes a solenoid |20 having an armature member IZIassociated therewith and in the form of a pin adapted to be movedagainst an extension |22 of valve 8.1. The solenoid has a line |23connected therewith and this line leads to contact |24 on the floorboard. Battery |25 is connected by line |26 with contact |21 and contact|28 is connected by line |29 to contact |3. Contacts |21 and |28 arearranged to be closed by a dash switch I3I and contacts |30 and |24 arearranged to be closed by switch |32 fixed on the accelerator pedal andeffective only while the accelerator pedal is in overtravel position,that is, beyond wide open throttle position. Thus, by pressing theaccelerator pedal down beyond wide open throttle position the circuit tothe solenoid is established whereupon the pin |2| will be moved upwardlyto shift valve 8| to closed position. Switch |3| may be the ignitionswitch for the motor vehicle engine located on the instrument panel |33of the vehicle. As long as the pedal is maintained in oyertravelposition the planetary gearing will remain in geared drive and as soonas the pedal is released from overtravel position vand the. vehicle isabove the governed speed then valve 31 will return to its open positionwhereupon the clutch device 35 will again become effective.

Shift lever 65 is operated by Bowden wire IM extending through theinstrument board and having a knob |35 on its end by means of which thedriver can shift to select forward or reverse drive and neutral, suchpositions being indicated by letters F, N and R in Fig. 3. The shiftlever 55 has a ball shaped end |35 extending through a slot |31 in shiftrod 68 and engaging in a recess in sleeve valve |33. Collar |33 andshifter yoke 59 are fixed on rod B8. Springs |40 and HII surround theshaft 68 and exert an equal opposed pressure whereby sleeve |38 and theshift rod are normally urged to neutral position as shown in Fig. 4.Spring |40 bears at one end against collar |39 and at the other againstsleeve |38 while spring |4| bears at one end against yoke 69 and at theother end against the sleeve valve |38. The sleeve valve has asemicircular outlet groove |42 with which a smaller inlet groove |43communicates. When groove |43 registers with conduit 6| the sleeve |38is in neutral position so that fluid will ilow through groove |45 tobranch conduit 63 and chamber 52 to apply the synchronizer brake 54 andthereby hold shaft I9 stationary. Movement of lever 65 will cause theend |36` to shift the sleeve |38 axially to move groove |43 out ofregistration with conduit 6| and will cause groove |42 to register witheither vent port |44 or |45 in casing l0 depending upon the direction ofshift. At the same time either spring |40'or |4| will be compressed toshift rail 68 to engage the forward or reverse clutch teeth just priorto venting the brake chamber 52. In the event the clutch teeth abut, thecompressed spring will force the clutch teeth into engagement uponrelease of shaft I9. Thus the clutch teeth will be engaged withoutclash. This synchronizing or braking of the driven shaft during forwardand reverse selection is covered in my co-pending application Serial No.644,319, filed January 30, 1946, now Patent #2,559,128, July 3, 1951.

It will be understood that various forms of the invention other thanthose described above may be used without departing from the spirit orscope of the invention.

What i s claimed is:

1. In a transmission for motor vehicles driven by an engine having afuel intake manifold and controlled by an accelerator pedal, a powershaft driven by the engine, a driven shaft, planetary gearing connectingsaid shafts and having reaction means, reverse gearing driven from theplanetary gearing, a drive selection shift lever for the transmission, aprimary valve in the system operative by the shift lever, said valvebeing closed in neutral position and open in forward and reversepositions of the shift lever, a brake device for the reaction means, apressure fluid system connected to apply the brake device, a valvedevice controlling fluid flow to the brake device, conduit means leadingfrom the engine manifold to the valve device whereby manifold pressureis transmitted to the valve device to effect the opening thereof, anormally closed valve in the conduit means, and means operating inconjunction with the accelerator pedal for opening the conduit valvewhen the pedal is depressed beyond engine idling position.

2. In a transmission for motor vehicles driven by an engine having afuel intake manifold, a power shaft driven by the engine, a drivenshaft, planetary gearing adapted to drivingly connect said shafts andhaving a carrier, a reaction member, an overrunning brake between thecarrier and the reaction member, a clutch for effecting unitary rotationof the gearing, a pressure fluid system leading to the brake and theclutch, means in the system for opening the brake control valve whilethe engine is running above idling speed, a valve in the systemcontrolling fluid flow to the clutch, a spring normally closing saidvalve, means responsive to manifold pressure and vehicle speed opposingsaid spring pressure and tending to open the valve, and electricallyenergized means operable at will for overruling the means responsive tomanifold pressure and vehicle speed to close the valve.

3. In a transmission for motor vehicles driven by an engine having afuel intake manifold, a power shaft driven by the engine, a drivenshaft, planetary gearing adapted to drivingly connect said shafts andhaving a carrier, a reaction member, an overrunning brake between thecarrier and the reaction member, a clutch for effecting unitary rotationof the gearing, a pressure fluid system leading to the brake and theclutch, means in the system for opening the brake control valve whilethe engine is running above idling speed, a valve in the systemcontrolling fluid flow to the clutch, a spring normally closing saidValve, means responsive to manifold pressure and vehicle speed opposingsaid spring pressure and tending to open the valve, and a solenoidadapted to be energized at will by the vehicle driver for overruling themeans responsive to manifold pressure and vehicle speed to close thevalve.

4. In a transmission for motor vehicles driven by an engine having afuel intake manifold and controlled by an accelerator pedal, said pedalhaving a normal operating movement and an additional movementovertraveling the normal movement, a power shaft driven by the engine, adriven shaft, planetary gearing adapted to drivingly connect said shaftsand having a carrier, a reaction member, an overrunning brake betweenthe carrier and the reaction member, a clutch for effecting unitaryrotation of the gearing, a pressure fluid system leading to the brakeand the clutch, a brake control valve in the system, means in the systemfor opening the brake control valve while the engine is running aboveidling speed, a valve in the system controlling fluid flow to theclutch, a spring normally closing said valve, means responsive tomanifold pressure and vehicle speed adapted to open the valve,electrically energized means for overruling the means responsive tomanifold pressure and vehicle speed to close the valve, and switch meansfor the electrically energized means adapted to be closed by theaccelerator pedal while in overtravel position.

5. In a transmission for motor vehicles driven by an engine, a powershaft driven by the engine, a driven shaft, planetary gearing adapted todrivingly connect said shafts and having a carrier, a reaction member,an overrunning brake between the carrier and the reaction member, acontrol brake for holding the reaction member stationary to effectgeared drive through the planetary gearing, a clutch engageable toeffect unitary rotation of the planetary gearing, a pressure fluidsystem for applying the brake and clutch, a normally closed valve in thesystem controlling fluid flow to the brake, a speed influenced valve inthe system controlling fluid flow to the clutch, and means connectingthe portion of the system between the clutch control valve and theclutch to the brake control valve whereby fluid pressure will hold thebrake control valve open while the clutch control valve is open.

6. In a transmission for motor vehicles driven by an engine, a powershaft driven by the engine, said engine having a fuel intake manifoldand an accelerator pedal, a driven shaft, planetary gearing adapted toconnect said shafts in geared drive and having a carrier, a reactionmember, an overrunning brake between the carrier and the reactionmember, a control brake for holding the reaction member stationary toeffectgeared drive through the planetary gearing, a clutch engageable toeffect unitary rotation of the planetary gearing, a pressure fluidsystem for applying the brake and clutch, a normally closed valve in thesystem controlling fluid flow to the brake, a conduit leading from themanifold to the brake control valve whereby manifold pressure may act toopen the brake valve, a normally closed valve in the conduit opened bythe accelerator pedal beyond idling position, a speed influenced valvein the system controlling fluid flow to the clutch, and means connectingthe portion of the system between the clutch control valve and theclutch to the brake control valve whereby fluid pressure will hold thebrake control valve open while the clutch control valve is open.

7. In a transmission for motor vehicles driven by an engine, a powershaft driven by the engine, said engine having an intake manifold, adriven shaft, planetary gearing adapted to drivingly connect said shaftsto rotate at different speeds and having a carrier, a reaction member,an overrunning brake between the carrier and the reaction member, acontrol brake for holding the reaction member stationary to effectgeared drive through the planetary gearing, a clutch engageable toeffect unitary rotation of the planetary gearing, a pressure fluidsystem for applying the brake and clutch, a normally closed valve in thesystem controlling fluid flow to the brake, a valve in the systemcontrolling fluid flow to the clutch, said valve being opened inresponse to vehicle speed and pressure in the manifold, and meansconnecting the portion of the system between the clutch control valveand the clutch to brake control valve whereby fluid pressure will holdthe brake control valve open while the clutch control valve is open.

8. In a transmission for motor vehicles driven by an engine, a powershaft driven by the engine, said engine having a fuel intake manifoldand an accelerator pedal, a driven shaft, planetary gearing interposedbetween said shafts and having a carrier, said gearing being controlledfor reduced or direct drive, a reaction member, an overrunning brakebetween the carrier and the reaction member, a control brake for holdingthe reaction member stationary to effect reduced drive through theplanetary gearing, a clutch engageable to effect unitary rotation of theplanetary gearing, a pressure fluid system for applying the brake andclutch, a normally closed valve in the system controlling fluid flow tothe brake, means for moving the valve to open position in response tomanifold pressure, a conduit connecting the manifold and valve, a valvein the conduit controlled by the accelerator pedal whereby manifoldpressure may open the brake control valve, a normally closed valve inthe system controlling fluid flow to the clutch, speed and manifoldpressure means for opening the clutch valve, and means connecting theportion of the system between the clutch control valve and the clutch tothe brake control valve whereby fluid pressure will hold the brakecontrol valve open while the clutch control valve is open.

FOREST R. MCFARLAND.

REFERENCES CITED The following references are of record in the flle ofthis patent:

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